The proposed research has two major aims. The first aim is to compare in strains of rats that vary in emotionality the effects of glucose (a sugar that readily crosses the blood-brain-barrier) and fructose (a sugar that does not readily cross the blood-brain-barrier) on memory. To address this aim we will characterize in strains of rats that differ in their glucose response to stressful events the dose-response curves for the effects of glucose on memory storage. Finding an orderly relationship between these dose-response curves and a strain's glucose response to stress would provide strong evidence that the level of emotionality covaries with the ability of glucose to modulate memory. We also will characterize the effect of fructose on the modulation of memory in these same strains, and we will investigate the effect of combined glucose and fructose treatment on memory storage. A finding of similar glucose and fructose dose-response curves within each strain would provide strong support for our suggestion that glucose and fructose share similar peripheral pathways for influencing memory modulation. The second aim of our research is to conduct in a single study a within-strain and between-strain investigation of the effects of glucose on memory storage, memory re-storage (reactivation), and memory retrieval. To establish both biological and behavioral markers of emotionality, we also will compare blood glucose concentrations and open-field activity levels under stressed versus unstressed conditions. Because in people with impaired memory (the elderly, Alzheimer's patients) glucose can enhance memory, it is expected that the further characterization and understanding of glucose?s modulatory effects that will be provided by our studies will have both practical and clinical significance.